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IronMosher

Spider Valve 212 Low Volumn after changing tubes

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Hey All,

I changed my Spider Valve 212 Tubes after one 6l6GC tube totally blew the the plastic vacuum seal.  It also blew some fuses (of course).  The last time I changed and biased the tubes I used thetubestore tubes with no problem.  I just changed the tubes with JJ tubes and the bias was almost perfect (34.9 and 35.1).  I also reset the computer this time.  Now the volume when totally cranked up on both (channel and master) is so low my strings are louder.  I removed the footswitch and all pedals just in case and it didn't make a difference.  None of the pots are crackling.  It does seem the tubes arent as bright and hot as the last ones.  Any thoughts? 

 

Much appreciated,

Iron Mosher

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1) 6L6GC is the wrong tube and therefore, probably the wrong bias. So yes, the fuse would blow.

     You can't use the same bias on a different tube, even in an all analog tube amp.

 

2) JJ's are also the wrong tube so the normal bias volts would be the wrong bias volts. 35mV +/- 2mV

      does not apply to other tubes in this amp.

 

3) Power tubes have to be matched pairs.

 

 

4) These are not all analog tube amps of old, these are hybrids (analog/digital), the two sections need to talk nice to each other.

      Not using the correct tubes and bias, undoes that. I don't want to see your amp on my repair bench. Use the specified tubes and bias.

      Please,...

 

 

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I figured JJ's were wrong.  Too long a story there.  I originally replaced the tubes with 6L6GC and they worked fine.  What should they be? I always buy matched pairs.  I have the old tubes and they read:  12AX7b (China) and 5881WXT (Soviek, Russian).  IS that what I should get?  Thetubestore.com when I called a few years ago said to use the 6L6CG and the Tung-Sol 12AX7.  Which worked great for a year or so.

 

Thanks again for the help.

 

 

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" 12AX7b (China) and 5881WXT (Soviek, Russian).  IS that what I should get? " --- Yes. 5881WXT power tubes have to be a matched set. 

 

" Thetubestore.com when I called a few years ago said to use the 6L6CG and the Tung-Sol 12AX7. " --- Yes, but for an "all analog" tube amp.

The characteristic curves are close, but not close enough. So the specified tubes have to be used.

 

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The internet and a guy from thetubestore.com both inform me that 6L6 and 5881 tubes are the same thing.  I've been running 6L6GC's for years.

 

The problem in this case was the 12ax7'S WERE NOT 12AX7B'S.  I put the old ones back in and everything works beautifully now.

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Don't use the 6L6GC,... forget what the guy from the Tube Store says, he's probably not an expert in hybrid amps like this,

so use the specified tubes. I worked on hundreds of these the past 14 years I've been here. The characteristic curves are

not close enough to be 100% drop-in swap. These are not all analog Marshal amps. Use the specified tubes.

 

12AX7's are less crucial, the B's are optimum, but EH's will do,.... just no JJ's.

 

Using 6L6GC or other unspecified tube is an unsupported modification to the amp. If this were to show up on my bench,

I might be told to send back untouched. I don't want to see that happen.

 

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